Bearing



J 2, 1945- I A. A. GRIFFITH 2,403,176

BEARING Filed 001;. 7, 194a Patented July 2, 1946 UNITED STATES PATENT OFFICE BEARING Alan Arnold Griffith, Derby, England, assignor to Rolls-Royce Limited, Derby, England, a British company Application October '1, 1943, Serial No. 505,390 In Great Britain April 15, 1941 .relatively rotatable rotors comprises a radial bearing for each rotor and thrust-bearings between adjacent rotors characterised in that the outer races of the radial bearings have plain cylindrical surfaces permitting slight axial movements, in combination with means for applying an axial loading to the complete assemblage. Preferably the thrust-bearings are engaged .by races formed on the sides of the outer races of the radial bearings.

According to another feature of this invention the material of the shaft whereon thebearingassemblage is mounted is selected to have a smaller co-efllcient of thermal expansion than the bearings assembled on it.

According to yet another feature of this invention, the axial preloading aforesaid is applied by a nut screwed onto the shaft, through a combined radialand thrust-bearing at the end of the assemblage, to the rotors and their interposed thrust bearings.

The accompanying drawing is a sectional elevation showing a preferred embodiment of this invention. a

Referring to this drawing, the reference H) indicates a shaft whereon there are mounted a plurality of rotor elements of which the end one is indicated at I l, and the others by the reference it. These elements are required to rotate in op- 3 Claims. (Cl. 308-174) rotors I2 is mounted on a radial or journal ballbearing whereof the inner race I3 is of the usual construction, but the outer race H is formed with a plain cylindrical surface I! to be engaged by the balls It. With this arrangement, the radial bearings effect no axial constraint on the rotors.

Between each pair of adjacent races 14 there is provided a ball thrust-bearing H.

The rotor II at the end of the assemblage is provided with a combined, radial and thrustbearing, whereof the inner race is shown at I8 and the outer race at I9 these being of any known construction suitable for applying an end-thrust to the assemblage. Such end-thrust is applied by means of a nut screwed onto the shaft l0 and engaging through suitable spacing-members 2| the inner race 18 of the bearing for the rotor Ii, and additional spacing-members 22' are provided posite directions on the shaft,vand when such a ,ditions of gyroscopic loading. the loading of the bearings will be always of the same sign and vary located between the outer races for the bearings for the respective rotor elements.

The material of the shaft I0 is selected to have a smaller co-efllcient of thermal expansion than the assemblage of races on it, so that when a certain value of preloading is applied at an I ordinary low atmospheric temperature, any increase of temperature increases the preloading owing to the differential expansion. In the case of a power-unit, this variation of preloading with temperature ensures the minimum of friction when starting up from cold and also an adequate preloading when the power-unit is running under its normal working conditions. There is no disadvantage in the reduced preloading during the starting period, since under normal circumstances the problem of the gyroscopic forces does not arise at that time, but it is rendered available before it is required when the aircraft is in flight. Another advantage of the construction above described, is that the preloading is applied directly to the thrust-bearings so that the friction of the inner journal-races l3 does not resist the preloading. Finally, it will be appreciated that the general construction is an extremely simple one for solving the problem of adequately supporting rotor elements arranged as above described.

I claim:

only in magnitude. ,For this purpose each of the II 1. The combination of a shaft, a plurality of relatively rotatable co-axial rotors thereon, a

radial anti-friction bearing for each rotor having the inner surface of its outer races of plain cylinclrical form, spacing pieces between the inner races of said radial bearings, said shaft havin a lower co-efflcient of thermal expansion than the assemblage of inner races and spacing pieces on it, a plurality of axial thrust-bearings disposed respectively between the outer races of said radial bearings, and means for applying an axial loading to said rotors and thrust-bearings.

2. The combination of a shaft, a plurality of relatively rotatable co-axial rotors thereon, a radial anti-friction bearing for each rotor permitting axial movement thereof relatively to the shaft, a plurality of axial thrust-bearings disposed respectively between said rotors, a com- ,bined radial and thrust-bearing at one end of said plurality of rotors, and a nut screwed on said shaft to apply axial thrust to said last- 'mentioned bearing and through it to said rotors and thrust-bearings.

- 3. The combination of a shaft, a plurality-oi relatively rotatable co-axial rotors ,thereon, a radial anti-friction bearing for each rotor having the inner surface of its outer race of plain cylindrical form permitting axial movement thereof relatively to the shaft, spacing pieces between the inner races ofsaid radial bearings, said shaft I to said last-mentioned bearing and throughitto the assemblage of rotors on the shaft.

ALAN ARNOLD 012mm 

